Pneumatic Rotating Control Device Latch

ABSTRACT

A rotating control device can include an engagement member that secures relative to an outer housing an annular seal and/or a bearing, the member displacing in response to a pneumatic pressure differential. A method can include applying a pneumatic pressure differential, thereby displacing an engagement member that secures an annular seal relative to an outer housing, with rotation of the seal relative to the housing being permitted when the member is displaced to a position in which removal of the seal from the housing is prevented. A rotating control device can include a piston and an engagement member which secures an annular seal relative to an outer housing, the piston having piston areas exposable to a pneumatic pressure differential, and with increased pressure applied to another piston area of the piston displacing the piston to a position in which the member does not secure the seal relative to the housing.

TECHNICAL FIELD

This disclosure relates generally to equipment utilized and operations performed in conjunction with a subterranean well and, in one example described below, more particularly provides a rotating control device with a pneumatically operated latch.

BACKGROUND

A rotating control device (RCD, also known as a rotating head, rotating blowout preventer and rotating diverter) is used to seal off an annulus about a rotatable tubular (such as, part of a drill string or other tubular string) at or near the earth's surface. For this purpose, the rotating control device includes an annular seal, which may rotate with the tubular. If the annular seal does rotate, bearings can be used to allow the seal to rotate relative to an outer housing of the rotating control device.

It is beneficial to be able to releasably latch the seal and/or bearings relative to the outer housing, so that the seal and/or bearings can be conveniently installed and removed when desired. Thus, it will be appreciated that improvements are continually needed in the arts of constructing and operating latches for rotating control devices.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a representative cross-sectional view of a well system and associated method which can embody principles of this disclosure.

FIG. 2 is a representative cross-sectional view of the well system and method of FIG. 1, with a seal and bearing assembly latched into a rotating control device outer housing.

FIG. 3 is an enlarged scale representative cross-sectional view of the rotating control device, with the seal and bearing assembly positioned, but not latched, therein.

FIG. 4 is a representative cross-sectional view of the rotating control device, with the seal and bearing assembly latched therein.

FIG. 5 is a further enlarged scale representative cross-sectional view of a latch of the rotating control device, the latch being shown in an unlatched configuration.

FIG. 6 is a representative cross-sectional view of the latch, shown in a latched configuration.

FIG. 7 is a further enlarged scale representative cross-sectional view of an upper portion of a piston of the latch retained in an upwardly displaced, latched position.

FIG. 8 is a representative perspective view of the upper portion of the piston, apart from the remainder of the rotating control device.

FIG. 9 is a further enlarged scale representative cross-sectional view of a method of displacing the piston to an unlatched position.

FIGS. 10 & 11 are representative elevational views of examples of the piston and an engagement member of the latch.

DETAILED DESCRIPTION

FIG. 1 is a representative cross-sectional view of a well system 10 and associated method which can embody principles of this disclosure. However, it should be clearly understood that the system 10 and method are merely one example of an application of the principles of this disclosure in practice, and a wide variety of other examples are possible. Therefore, the scope of this disclosure is not limited at all to the details of the system 10 and method described herein and/or depicted in the drawings.

In the FIG. 1 example, a rotating control device (RCD) 12 is connected as part of a riser string 14, so that a flow passage 16 of the riser string extends longitudinally through the RCD. The RCD 12 is connected between an annular blowout preventer (BOP) 18 and a diverter tie-back 20. However, in other examples, the RCD 12 is not necessarily connected as part of a riser string (e.g., the RCD could be used with a land-based rig), and the RCD is not necessarily connected between any particular well tools or components.

The BOP 18 can be connected to various types of structures 22 (for example, a tensioner ring of the riser string 14, a wellhead or a lower marine riser package (LMRP)), so that the passage 16 is in communication with a wellbore (not shown). The diverter tie-back 20 can be connected to a rig diverter (not shown) of a floating or jack-up drilling rig. However, the scope of this disclosure is not limited to use of the RCD 12 with any particular type of drilling rig, or to any particular arrangement or configuration of components or well tools above or below the RCD.

The RCD 12 includes a pneumatically operated latch 24 for releasably securing a seal and bearing assembly (see FIG. 2) in an outer housing 26 of the RCD. As used herein, the term “pneumatic” refers to the use of gaseous fluid (such as, pressurized air, nitrogen, or other gases or combinations of gases) to operate a device.

In FIG. 1, it can be seen that the latch 24 includes an engagement member 28 positioned in the outer housing 26. In other examples, multiple circumferentially distributed engagement members could be used. Thus, the scope of this disclosure is not limited to use of any particular number or configuration of engagement member(s).

The engagement member 28 of FIG. 1 is in a radially outwardly disposed position. In this position, the latch 24 allows for removing and/or inserting the seal and bearing assembly (see FIG. 2) in the RCD 12.

FIG. 2 is a representative cross-sectional view of the well system 10 and method of FIG. 1, with a seal and bearing assembly 30 latched into the rotating control device outer housing 26. In this configuration, annular seals 32 of the assembly 30 can sealingly engage an exterior of a tubular 34 (such as a drill pipe) inserted in the passage 16.

The assembly 30 includes bearings 36, which permit the seals 32 to rotate relative to the outer housing 26. In this manner, the seals 32 can rotate with the tubular 34 while sealing off an annular space 38 formed radially between the tubular and the outer housing 26. The latch 24 releasably secures the assembly 30 against removal from the outer housing 26.

In the FIGS. 1 & 2 example, the latch 24 releasably secures both the seals 32 and the bearings 36 against removal from the RCD 12. However, in other examples, the latch 24 could releasably secure only the seals 32, or only the bearings 36 (e.g., if the seal is separately removable from the outer housing 26). Thus, the scope of this disclosure is not limited to use of any particular type of seal and bearing assembly, or to use of an assembly which includes both seals and bearings.

Two seals 32 are depicted in FIG. 2, and the seals are illustrated as being of the type known to those skilled in the art as a “passive” seal. However, in other examples, a single seal could be used, and some or all of the seals could be “active” seals. The seals 32 are not necessarily positioned within the outer housing 26. Thus, it will be appreciated that the scope of this disclosure is not limited to use of any particular number, position or type(s) of annular seals.

As described more fully below, the latch engagement member 28 can be displaced radially relative to the outer housing 26 between a position in which removal of the seal and bearing assembly 30 from the RCD 12 is prevented (as in FIG. 2), and a position in which the seal and bearing assembly can be inserted into, or removed from, the outer housing 26 (as in FIG. 1).

FIG. 3 is an enlarged scale representative cross-sectional view of the rotating control device 12, with the seal and bearing assembly 30 positioned (but not latched) therein. In this example, only a single annular seal 32 is used.

Note that seals 40 carried on the seal and bearing assembly 30 are sealingly engaged in a bore of the housing 26. The seals 40 seal radially between the housing 26 and the seal and bearing assembly 30.

The seals 40 longitudinally straddle the engagement member 28. In this manner, well fluids and debris are effectively isolated from the engagement member 28 while the seal and bearing assembly 30 is positioned in the housing 26, thereby preventing such well fluids and debris from hindering displacement of the engagement member.

FIG. 4 is a representative cross-sectional view of the rotating control device 12, with the seal and bearing assembly 30 latched therein. In this view, it may be seen that the engagement member 28 is displaced radially inward into engagement with an annular recess 42 on the seal and bearing assembly 30, thereby securing the seal and bearing assembly in the outer housing 26. If the bearings 36 are not used (e.g., if the seal 32 does not rotate), then the recess 42 could be formed on a housing or mandrel that supports the seal.

A piston 44 of the latch 24 is displaced upwardly, in order to displace the engagement member 28 radially inward. In other examples, the piston 44 could be displaced downwardly to displace the engagement member 28 inward. Thus, the scope of this disclosure is not limited to any particular configuration or direction of displacement of any components of the latch 24.

In the FIG. 4 example, the piston 44 is displaced upwardly and downwardly in response to pneumatic pressure differentials applied to the piston via ports 46, 48 formed in the outer housing 26. To displace the piston 44 upwardly, so that the engagement member 28 is displaced inwardly and the assembly 30 is secured in the outer housing 26, increased pneumatic pressure can be applied to the port 46. To displace the piston 44 downwardly, so that the engagement member 28 is displaced outwardly and the assembly 30 is not secured in the outer housing 26, increased pneumatic pressure can be applied to the port 48.

FIG. 5 is a further enlarged scale representative cross-sectional view of the latch 24 of the rotating control device 12, the latch 24 being shown in an unlatched configuration. For clarity of illustration and description, the seal and bearing assembly 30 (see FIG. 4) are not shown in FIG. 5.

The piston 44 is depicted in FIG. 5 in its downwardly displaced position. In this position, the engagement member 28 is permitted to expand radially outward, so that the seal and bearing assembly 30 can be inserted into, or removed from, the outer housing 26.

In this example, the engagement member 28 is initially constructed in its radially outwardly expanded configuration and, although it may be deformed radially inward into engagement with the seal and bearing assembly 30 as described above (see FIG. 4), due to its resilience the engagement member “wants” to return to the radially outwardly expanded configuration. The engagement member 28 is provided with alternating upwardly and downwardly extending circumferentially spaced apart slots 50 to enhance its resilience, and to prevent excessive stresses in the engagement member.

In other examples, multiple engagement members could be provided without the slots 50, and/or biasing devices (such as, springs or other mechanical devices) could be provided to bias the engagement member(s) toward their unlatched position(s). Thus, the scope of this disclosure is not limited to any particular structural or operational features of the engagement member 28 depicted in the drawings and described herein.

The piston 44 has opposing annular piston areas 52, 54 formed thereon. Pressure differentials applied via the ports 46, 48 act on these piston areas 52, 54. Seals 56 carried externally on the piston 44 isolate the piston areas 52, 54 and the respective ports 46, 48 from each other in the housing 26, so that appropriate pressure differentials can be maintained across the piston to displace it upwardly or downwardly.

Additional seals 58 are provided in the FIG. 5 example to prevent well fluids and debris from hindering displacement of the piston 44. In a contingency operation (such as, in the event that the piston 44 cannot be displaced in response to a pressure differential applied to the piston areas 52, 54), increased pressure can be applied to an annular piston area 60 (at an upper end of the piston and radially between the seals 56, 58) to downwardly displace the piston, and/or increased pressure can be applied to an annular piston area 62 (at a lower end of the piston and radially between the seals 56, 58) to upwardly displace the piston. Since the piston areas 60, 62 are much larger than the piston areas 52, 54, this contingency operation should result in increased force being applied to the piston 44 due to the applied pressure.

Of course, it is not necessary for the piston areas 60, 62 to be greater than the piston areas 52, 54 (since, for example, pressure differentials can be applied to both sets of piston areas to increase the force applied to the piston 44, and/or the pressure differential(s) can be increased to increase the force applied to the piston), and it is not necessary for the piston areas 60, 62 to be provided at all. Thus, the scope of this disclosure is not limited to use of any particular number or configuration of piston areas on the piston 44.

FIG. 6 is a representative cross-sectional view of the latch 24, shown in a latched configuration. The engagement member 28 has been displaced radially inward due to upward displacement of the piston 44.

The piston 44 has a conical ramp 64 formed therein which biases the engagement member 28 radially inward as the piston 44 displaces upward. Although the seal and bearing assembly 30 is not shown in FIG. 6, it will be appreciated that, as the engagement member 28 displaces radially inward, it will engage the recess 42 (see FIG. 4) and thereby prevent removal of the seal and bearing assembly from the outer housing 26.

Note that an increased pressure is applied to the port 46 as compared to pressure at the port 48, in order to apply a pressure differential to the piston areas 52, 54 and thereby displace the piston 44 upward. It is, in this example, desirable for the piston 44 to not inadvertently displace downward (due to the force of gravity) to its FIG. 5 unlatched position, because this would allow the engagement member 28 to displace radially outward, and would thus allow the seal and bearing assembly 30 (see FIG. 3) to be displaced out of the housing 26.

In order to prevent inadvertent downward displacement of the piston 44, the pressure differential can remain applied to the piston areas 52, 54 (e.g., with greater pressure being applied to the port 46 as compared to the port 48). However, pressure sources can unexpectedly fail to maintain desired pressures (for example, a pump could malfunction, a pressure delivery line could burst, etc.), and so it is desired, in this example, to provide a way to prevent inadvertent downward displacement of the piston 44, without relying on maintenance of pressure.

FIG. 7 is a further enlarged scale representative cross-sectional view of an upper portion of the piston 44 of the latch 24 retained in an upwardly displaced, latched position. The piston 44 is retained in this position by means of circumferentially distributed retainer members 66 (only one of which is visible in FIG. 7) formed on the upper portion of the piston.

The retainer members 66 releasably engage an annular recess 68 formed in the outer housing 26. The retainer members 66 are resilient and can be disengaged from the recess 68 when a sufficient downwardly directed force acts on the piston 44, for example, when a pressure differential is applied to the piston areas 52, 54 to downwardly displace the piston (see FIG. 5).

In this example, it is preferred for the force which causes the retainer members 66 to disengage from the recess 68 to be greater than the force of gravity acting on the piston 44. In this manner, the piston 44 will not inadvertently displace downward from its upwardly displaced latched position.

FIG. 8 is a representative perspective view of the upper portion of the piston 44, apart from the remainder of the rotating control device 12. In this view, the manner in which the retainer members 66 are formed and circumferentially distributed on the upper portion of the piston 44 can be clearly seen.

In other examples, other types and/or numbers of releasable retainers (such as, a snap ring) may be used instead of the retainer members 66. In addition, it is not necessary for the retainer members 66 or other releasable retainer to be positioned at an upper portion of the piston 44. Thus, the scope of this disclosure is not limited to any particular number, position or configuration of a releasable retainer, and the use of a releasable retainer is not necessary at all.

FIG. 9 is a further enlarged scale representative cross-sectional view of a method of displacing the piston 44 to an unlatched position. The method depicted in FIG. 9 may be used as a contingency measure, in the event that a pressure differential applied to the piston areas 52, 54 cannot displace the piston 44 downwardly to its unlatched position.

In the FIG. 9 example, a threaded opening 70 is provided in the outer housing 26. The threaded opening 70 may be used as a port to apply increased pneumatic or hydraulic pressure to the piston area 60, thereby forcing the piston 44 to displace downwardly.

As another alternative, a threaded member 72 may be threaded into the opening 70, so that the threaded member contacts the upper portion of the piston 44. Further threading of the member 72 into the opening 70 can apply a downwardly directed force to downwardly displace the piston 44 to its unlatched position.

FIG. 10 is a representative elevational view of one example of the piston 44 and the engagement member 28 of the latch 24. The piston 44 and engagement member 28 are shown in FIG. 10 from an interior view, apart from the remainder of the rotating control device 12.

In this example, the engagement member 28 is circumferentially continuous and multiple wedges 74 are positioned on an interior surface of the piston 44, so that the wedges engage the upwardly facing slots 50 formed in the engagement member when the piston displaces downwardly toward its unlatched position. In this manner, the wedges 74 force the slots 50 to spread apart, thereby causing the circumferentially continuous engagement member 28 to radially outwardly expand.

The wedges 74 may be used in addition to, or in place of, the resilience of the engagement member 28 (as discussed above) to cause the engagement member to displace outwardly to its unlatched configuration. Any number, position, spacing or configuration of wedges may be used, and it is not necessary for the wedges 74 to be used at all, in keeping with the principles of this disclosure.

FIG. 11 is a representative elevational view of another example of the piston 44 and the engagement member 28 of the latch 24. In this example, the engagement member 28 is not circumferentially continuous, but instead has a gap 78 therein. The engagement member 28 of FIG. 11 is, thus, a C-shaped member.

Only a single wedge 74 is carried on the piston 44 in the FIG. 11 example. The wedge 74 is received in the gap 78.

When the piston 44 displaces downward to its unlatched position, the wedge 74 forces the gap 78 to widen, thereby causing the engagement member 28 to radially outwardly expand. The wedge 74 may be used in addition to, or in place of, the resilience of the engagement member 28 (as discussed above) to cause the engagement member to displace outwardly to its unlatched configuration.

It may now be fully appreciated that the above disclosure provides significant advances to the art of constructing and operating rotating control devices. In examples described above, a latch 24 can be conveniently and reliably operated using pneumatic pressure.

The above disclosure provides to the art a rotating control device 12. In one example, the rotating control device 12 can comprise an outer housing 26, at least one annular seal 32 and a latch 24 including at least one engagement member 28 which releasably secures the annular seal 32 and/or a bearing 36 relative to the outer housing 26. The engagement member 28 displaces in response to a pneumatic pressure differential.

The engagement member 28 may displace in further response to displacement of a piston 44 exposed to the pneumatic pressure differential. The piston 44 may displace upwardly against gravity to a position in which the engagement member 28 secures the annular seal 32 and/or the bearing 36 relative to the outer housing 26.

The rotating control device 12 can also include a retainer member 66 which releasably retains the piston 44 in the upwardly displaced position.

The piston 44 may displace to a position in which the engagement member 28 does not secure the annular seal 32 and/or the bearing 36 relative to the outer housing 26. In this example, a wedge 74 may bias the engagement member 28 to displace in response to the displacement of the piston 44 to the position.

The piston 44 can include first and second piston areas 52, 54 exposable to the pneumatic pressure differential. Increased pressure applied to a third piston area 60 of the piston 44 may be used to displace the piston 44 to a position in which the engagement member 28 does not secure the annular seal 32 and/or the bearing 36 relative to the outer housing 26.

The rotating control device 12 can include seals 58 which straddle the engagement member 28 and sealingly engage between the outer housing 26 and a seal and bearing assembly 30 which includes the bearing 36.

A method of releasably latching at least one annular seal 32 relative to an outer housing 26 of a rotating control device 12 is also described above. In one example, the method comprises: applying a pneumatic pressure differential to a latch 24 of the rotating control device 12, thereby displacing an engagement member 28 that releasably secures the annular seal 32 relative to the outer housing 26. Rotation of the annular seal 32 relative to the outer housing 26 is permitted when the engagement member 28 is displaced to a position in which removal of the annular seal 32 from the outer housing 26 is prevented.

In the method, a bearing 36 may provide for rotation of the annular seal 32 relative to the outer housing 26. The step of displacing the engagement member 28 can releasably secure the bearing 36 relative to the outer housing 26.

The method may include rotating a threaded member 72, thereby displacing the engagement member 28 to a position in which removal of the annular seal 32 from the outer housing 26 is permitted.

The step of displacing the engagement member 28 can include displacing a piston 44 exposed to the pneumatic pressure differential. The step of displacing the piston 44 can include displacing the piston 44 upwardly against gravity. The step of displacing the piston 44 upwardly can include engaging a retainer member 66, thereby releasably retaining the piston 44.

The method may include displacing the piston 44 to a position in which the engagement member 28 does not secure the annular seal 32 relative to the outer housing 26, thereby causing a wedge 74 to bias the engagement member 28 outwardly.

In one example, a rotating control device 12 described above can comprise: an outer housing 26, at least one annular seal 32, and a latch 24 including a piston 44 and an engagement member 28 which releasably secures the annular seal 32 relative to the outer housing 26. The piston 44 may have first and second piston areas 52, 54 exposable to a pneumatic pressure differential, and increased pressure applied to a third piston area 60 of the piston 44 may displace the piston 44 to a position in which the engagement member 28 does not secure the annular seal 32 relative to the outer housing 26.

Although various examples have been described above, with each example having certain features, it should be understood that it is not necessary for a particular feature of one example to be used exclusively with that example. Instead, any of the features described above and/or depicted in the drawings can be combined with any of the examples, in addition to or in substitution for any of the other features of those examples. One example's features are not mutually exclusive to another example's features. Instead, the scope of this disclosure encompasses any combination of any of the features.

Although each example described above includes a certain combination of features, it should be understood that it is not necessary for all features of an example to be used. Instead, any of the features described above can be used, without any other particular feature or features also being used.

It should be understood that the various embodiments described herein may be utilized in various orientations, such as inclined, inverted, horizontal, vertical, etc., and in various configurations, without departing from the principles of this disclosure. The embodiments are described merely as examples of useful applications of the principles of the disclosure, which is not limited to any specific details of these embodiments.

In the above description of the representative examples, directional terms (such as “above,” “below,” “upper,” “lower,” etc.) are used for convenience in referring to the accompanying drawings. However, it should be clearly understood that the scope of this disclosure is not limited to any particular directions described herein.

The terms “including,” “includes,” “comprising,” “comprises,” and similar terms are used in a non-limiting sense in this specification. For example, if a system, method, apparatus, device, etc., is described as “including” a certain feature or element, the system, method, apparatus, device, etc., can include that feature or element, and can also include other features or elements. Similarly, the term “comprises” is considered to mean “comprises, but is not limited to.”

Of course, a person skilled in the art would, upon a careful consideration of the above description of representative embodiments of the disclosure, readily appreciate that many modifications, additions, substitutions, deletions, and other changes may be made to the specific embodiments, and such changes are contemplated by the principles of this disclosure. For example, structures disclosed as being separately formed can, in other examples, be integrally formed and vice versa. Accordingly, the foregoing detailed description is to be clearly understood as being given by way of illustration and example only, the spirit and scope of the invention being limited solely by the appended claims and their equivalents. 

What is claimed is:
 1. A rotating control device, comprising: an outer housing; at least one annular seal in a passage extending through the outer housing; and a latch in the outer housing, the latch including at least one engagement member which releasably secures relative to the outer housing at least one of a group comprising the annular seal and a bearing, wherein the engagement member displaces radially in response to a pneumatic pressure differential.
 2. The rotating control device of claim 1, wherein the engagement member displaces in further response to displacement of a piston exposed to the pneumatic pressure differential.
 3. The rotating control device of claim 2, wherein the piston displaces upwardly against gravity to a position in which the engagement member secures relative to the outer housing the at least one of the group comprising the annular seal and the bearing.
 4. The rotating control device of claim 3, further comprising a retainer member which releasably retains the piston in the upwardly displaced position.
 5. The rotating control device of claim 2, wherein the piston displaces to a position in which the engagement member does not secure relative to the outer housing the at least one of the group comprising the annular seal and the bearing, and wherein a wedge biases the engagement member to displace in response to the displacement of the piston to the position.
 6. The rotating control device of claim 2, wherein the piston includes first and second piston areas exposable to the pneumatic pressure differential, and wherein increased pressure applied to a third piston area of the piston displaces the piston to a position in which the engagement member does not secure relative to the outer housing the at least one of the group comprising the annular seal and the bearing.
 7. The rotating control device of claim 1, further comprising seals which straddle the engagement member and sealingly engage between the outer housing and a seal and bearing assembly which includes the bearing.
 8. A method of releasably latching at least one annular seal relative to an outer housing of a rotating control device, the method comprising: applying a pneumatic pressure differential to a latch of the rotating control device, thereby displacing an engagement member that releasably secures the annular seal relative to the outer housing, and wherein rotation of the annular seal relative to the outer housing is permitted when the engagement member is displaced to a position in which removal of the annular seal from the outer housing is prevented.
 9. The method of claim 8, further comprising a bearing which provides for rotation of the annular seal relative to the outer housing, and wherein the displacing the engagement member also releasably secures the bearing relative to the outer housing.
 10. The method of claim 8, further comprising rotating a threaded member, thereby displacing the engagement member to a position in which removal of the annular seal from the outer housing is permitted.
 11. The method of claim 8, wherein the displacing the engagement member further comprises displacing a piston exposed to the pneumatic pressure differential.
 12. The method of claim 11, wherein the displacing the piston further comprises displacing the piston upwardly against gravity.
 13. The method of claim 12, wherein the displacing the piston upwardly comprises engaging a retainer member, thereby releasably retaining the piston.
 14. The method of claim 11, further comprising displacing the piston to a position in which the engagement member does not secure the annular seal relative to the outer housing, thereby causing a wedge to bias the engagement member outwardly.
 15. A rotating control device, comprising: an outer housing; at least one annular seal; and a latch including a piston and an engagement member which releasably secures the annular seal relative to the outer housing, the piston having first and second piston areas exposable to a pneumatic pressure differential, and wherein increased pressure applied to a third piston area of the piston displaces the piston to a position in which the engagement member does not secure the annular seal relative to the outer housing.
 16. The rotating control device of claim 15, wherein the engagement member displaces to a position in which the engagement member secures the annular seal relative to the outer housing in response to exposure of the first and second piston areas to the pneumatic pressure differential.
 17. The rotating control device of claim 15, wherein the piston displaces upwardly against gravity to a position in which the engagement member secures the annular seal relative to the outer housing.
 18. The rotating control device of claim 17, further comprising a retainer member which releasably retains the piston in the upwardly displaced position.
 19. The rotating control device of claim 15, wherein a wedge biases the engagement member to displace in response to the displacement of the piston to the position in which the engagement member does not secure the annular seal relative to the outer housing.
 20. The rotating control device of claim 15, further comprising seals which straddle the engagement member and sealingly engage in the outer housing. 